Actually I have run into this problem myself. PS embeds a whole bunch of info ( file bloat) in the form of color profiles. Some browsers read this and make correction some don't . For example the same graphic probably appears fine in Safari or Chrome! If this is the case Try either of these methods and see which one is preferable to you.
1) make sure you have convert to sRGB checked.
2)you could use a utility like ImageAlpha to not only make the file smaller but get rid of the annoying extra data.
this will help your colors MATCH within the same screen. but the way each UA and platform interprets color varies , as does with the OS, and sometimes even just the monitor itself.